How to achieve this glaze effect

The glaze effect in the attached picture happened by happy accident where a 2nd glaze applied somewhat thickly to the top of the pot 'cracked' and the 1st glaze shows through. I like this and want more of the cracking next time. Any suggestions about technique or an additive to improve the chance that it will happen again?

This is fired to ^6 in electric kiln, and the glazes are Amaco PC Light Sepia over Deep Firebrick.

The glaze effect in the attached picture happened by happy accident where a 2nd glaze applied somewhat thickly to the top of the pot 'cracked' and the 1st glaze shows through. I like this and want more of the cracking next time. Any suggestions about technique or an additive to improve the chance that it will happen again?

This is fired to ^6 in electric kiln, and the glazes are Amaco PC Light Sepia over Deep Firebrick.

If the bottom glaze is shiny and the top glaze is matt, you can get this affect.TJR.